OBJECTIVE Demonstrate intratumoral genetic heterogeneity in rectal cancer. BACKGROUND Several clinical management decisions in rectal cancer may be influenced by pretreatment biopsy information. However, in the setting of significant intratumoral heterogeneity, biopsies may not be representative of the entirety of the tumor and limit the reliability of the information provided from them for clinical decision management. METHODS Three fragments from a single rectal adenocarcinoma were chosen for whole-exome sequencing followed by mutation detection analysis. About 25 Gb of unambiguously mapped sequences were generated for each sample resulting in a median fold-coverage of 35x. Captured sequences mapped to the reference human genome were then used for the detection of somatic point mutations. RESULTS Overall, 193 unique somatic point mutations were identified. Only 53 (27%) of these were shared by all three fragments, including known genes involved in early phases of the adenoma-carcinoma sequence (such as, APC). Approximately, 115 (59%) mutations were exclusively present in only one of the fragments, including mutations in "driver" genes (DNAH12). Jaccard distances showed a median distance of 0.603 for pair-wise comparison of fragments indicating significant heterogeneity between them. CONCLUSIONS Considerable intratumoral heterogeneity is present among naive rectal cancers. The majority of point mutations detected in different fragments from rectal cancers are frequently unique to a single fragment. These findings support that gene mutations found on single pretreatment biopsies will not necessarily be representative of mutations present in the entirety of the tumor and therefore may limit the utility of the biological information provided by single biopsy fragments for clinical management decisions.

Nonsyndromic cleft lip and palate (NSCL/P) is a complex disease resulting from failure of fusion of facial primordia, a complex developmental process that includes the epithelial-mesenchymal transition (EMT). Detection of differential gene transcription between NSCL/P patients and control individuals offers an interesting alternative for investigating pathways involved in disease manifestation. Here we compared the transcriptome of 6 dental pulp stem cell (DPSC) cultures from NSCL/P patients and 6 controls. Eighty-seven differentially expressed genes (DEGs) were identified. The most significant putative gene network comprised 13 out of 87 DEGs of which 8 encode extracellular proteins: ACAN, COL4A1, COL4A2, GDF15, IGF2, MMP1, MMP3 and PDGFa. Through clustering analyses we also observed that MMP3, ACAN, COL4A1 and COL4A2 exhibit co-regulated expression. Interestingly, it is known that MMP3 cleavages a wide range of extracellular proteins, including the collagens IV, V, IX, X, proteoglycans, fibronectin and laminin. It is also capable of activating other MMPs. Moreover, MMP3 had previously been associated with NSCL/P. The same general pattern was observed in a further sample, confirming involvement of synchronized gene expression patterns which differed between NSCL/P patients and controls. These results show the robustness of our methodology for the detection of differentially expressed genes using the RankProd method. In conclusion, DPSCs from NSCL/P patients exhibit gene expression signatures involving genes associated with mechanisms of extracellular matrix modeling and palate EMT processes which differ from those observed in controls. This comparative approach should lead to a more rapid identification of gene networks predisposing to this complex malformation syndrome than conventional gene mapping technologies.